1. Field of the Invention
The present invention relates to the field of opto-electronic devices.
2. Prior Art
The present invention is intended for use in opto-electronic devices, such as, by way of example, transmitters and receivers used in fiber-optic systems. On the transmitter side of a fiber optic system, a laser diode with laser diode driver circuitry and a monitor diode are generally packaged in a 3 pin TO-HEADER package, with a laser diode driver circuitry, typically a laser driver integrated circuit.
On the receiver side, transimpedance amplifiers are used to amplify the output of photodiodes receiving the optical signal. In such applications, the receiver in the fiber optic communications system typically comprises a photodiode and a preamplifier in a four pin header package, the preamplifier typically being a transimpedance amplifier to provide a voltage output responsive to the photodiode current output. The typical four pin package devotes two pins to power input and two pins to a differential output. However, new standards are requesting diagnostic functions from the optical preamplifier, such as a received signal strength indication (RSSI). A received signal strength indication signal is not difficult to generate within the preamplifier, though using conventional techniques, would require additional pins, or at least one additional pin, to bring out the RSSI signal.